adenylation (A) domain of linear gramicidin synthetase (LgrA) and similar proteins
This family of the adenylation (A) domain of nonribosomal peptide synthases (NRPS) includes linear gramicidin synthetase (LgrA) in Brevibacillus brevis. LgrA has a formylation domain fused to the N-terminal end that formylates its substrate for linear gramicidin synthesis to proceed. This formyl group is essential for the clinically important antibacterial activity of gramicidin by enabling head-to-head gramicidin dimers to make a beta-helical pore in gram-positive bacterial membranes, allowing free passage of monovalent cations, destroying the ion gradient and killing bacteria. This family also includes bacitracin synthetase 1 (known as ATP-dependent cysteine adenylase or BA1); it activates cysteine, incorporates two D-amino acids, releases and cyclizes the mature bacitracin, an antibiotic that is a mixture of related cyclic peptides that disrupt gram positive bacteria by interfering with cell wall and peptidoglycan synthesis. Also included is surfactin synthetase which activates and polymerizes the amino acids Leu, Glu, Asp, and Val to form the antibiotic surfactin.
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